1. Field of the Invention
The present invention relates to a method for the artificial cultivation of Lentinus edodes by using an artificial solid culture medium (hereinafter referred to as "cultural medium"), in which Lentinus edodes can successfully be harvested in a short time in large quantities.
2. Description of the Prior Art
In general, Lentinus edodes has heretofore been cultivated by the so-called bed log cultivation method using raw wood. However, since this bed log cultivation method is a natural cultivation method in which a long time, such as about 1.5 years, is required from the time of inoculation of the fungus seed to generation of a fruit body, the cultivation results are inevitably influenced by weather conditions and are very erratic. Further, the cultivation is often inhibited by injurious fungi and the harvest is frequently reduced by such damage. Furthermore, the price of raw wood is increasing because of the shortage thereof and the problem of the shortage of manpower in rural and mountain districts is becoming serious.
Accordingly, it has been desired to develop a method of cultivating Lentinus edodes in which raw wood is not used and a good harvest can be obtained on a regular and stable basis in a relatively short time without the need for extensive manual labor. However, an artificial cultivation method comparable to the bed leg cultivation method from the economic viewpoint was not found, prior to our invention. More specifically, various methods for artificially cultivating Lentinus edodes have heretofore been proposed, but they are defective in that a long time is required for cultivation and very complicated operations must be performed. Moreover, it often happens that no fruit bodies grow at all or if fruit bodies grow, the harvest thereof is small and most of the fruit bodies are deformed and have low commercial value. Therefore, the prior methods are not suitable as a technique for replacing the bed log cultivation method.
In contrast, for cultivation of other mushrooms such as Pholiota nameko and Pleurotus ostreatus, artificial methods are mainly used in place of the bed log cultivation method. If Lentinus edodes is cultivated following the artificial cultivation methods used for cultivating these other mushrooms, economical results cannot substantially be expected, apparently because the biological properties of Lentinus edodes are significantly different from those of Pholiota nameko, Pleurotus ostreatus and the like.
When the state of growth of Lentinus edodes in the bed log cultivation method is carefully examined, it is seen that, as shown in FIG. 1, most of the fruit bodies 3 grow from the bark face 1 and in general, fruit bodies do not grow from the cut end 2. In contrast, in the bed log cultivation of Pholiota nameko and Pleurotus ostreatus, fruit bodies grow well not only from the bark face but also from the cut end. It is considered that in case of Lentinus edodes, differentiation of hyphae to fruit bodies takes place only on the bark face, but in the case of Pholiota nameko and Pleurotus ostreatus, differentiation is possible if only hyphae grow and gather. That is, Lentinus edodes is substantially different from Pholiota nameko, Pleurotus ostreatus and the like with respect to differentiation of hyphae to fruit bodies. Accordingly, it is considered that Pholiota nameko, Pleurotus ostreatus and the like grow even on the surface of a culture medium which is not equivalent to the bark face of a log (namely, under the same conditions as those on the cut end of the log), but Lentinus edodes scarcely grows from the surface of such a culture medium. According to various artificial cultivation methods heretofore proposed, it is intended to cause fruit bodies of Lentinus edodes to grow, contrary the effects of nature, on the surface of a culture medium where spontaneous growth of fruit bodies is substantially difficult and therefore, a long time is required for cultivation, deformed fruit bodies are obtained and other serious defects occur.
As regards the role of the bark in the bed log cultivation of Lentinus edodes, there have been proposed various theories, for example, a theory of catalytic stimulus, a theory of nourishment and a theory of pressure stimulus. We have departed from these theories and, as a result of our studies, we have arrived at the conclusion that the bark has the role of adjusting the amount of air that permeates into the places where the rudiments of the Lentinus edodes fruit bodies form (namely, the zone between the bark and the xylem).